From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.90_1) id 1rhX6A-00025l-4T for mharc-qemu-trivial@gnu.org; Tue, 05 Mar 2024 10:53:00 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rhX5o-0001n3-CU; Tue, 05 Mar 2024 10:52:37 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rhX5l-0007X6-8k; Tue, 05 Mar 2024 10:52:36 -0500 Received: from mail.maildlp.com (unknown [172.18.186.31]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Tq0Lw2dv5z6J67f; Tue, 5 Mar 2024 23:47:36 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id 27DA9140F92; Tue, 5 Mar 2024 23:52:20 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Tue, 5 Mar 2024 15:52:19 +0000 Date: Tue, 5 Mar 2024 15:52:18 +0000 From: Jonathan Cameron To: Thomas Huth CC: , Fan Ni , "Michael S. Tsirkin" , Marcel Apfelbaum , Subject: Re: [PATCH 3/3] hw/mem/cxl_type3: Fix problem with g_steal_pointer() Message-ID: <20240305155218.00000c00@Huawei.com> In-Reply-To: <4f6e1748-a917-4b2b-847d-fbfe04a3e43e@redhat.com> References: <20240304104406.59855-1-thuth@redhat.com> <20240304104406.59855-4-thuth@redhat.com> <20240304151037.00000f6c@Huawei.com> <4f6e1748-a917-4b2b-847d-fbfe04a3e43e@redhat.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml100006.china.huawei.com (7.191.160.224) To lhrpeml500005.china.huawei.com (7.191.163.240) Received-SPF: pass client-ip=185.176.79.56; envelope-from=jonathan.cameron@huawei.com; helo=frasgout.his.huawei.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 05 Mar 2024 15:52:45 -0000 On Tue, 5 Mar 2024 08:27:52 +0100 Thomas Huth wrote: > On 04/03/2024 16.10, Jonathan Cameron wrote: > > On Mon, 4 Mar 2024 11:44:06 +0100 > > Thomas Huth wrote: > > =20 > >> When setting GLIB_VERSION_MAX_ALLOWED to GLIB_VERSION_2_58 or higher, > >> glib adds type safety checks to the g_steal_pointer() macro. This > >> triggers errors in the ct3_build_cdat_entries_for_mr() function which > >> uses the g_steal_pointer() for type-casting from one pointer type to > >> the other (which also looks quite weird since the local pointers have > >> all been declared with g_autofree though they are never freed here). > >> Fix it by using a proper typecast instead. For making this possible, we > >> have to remove the QEMU_PACKED attribute from some structs since GCC > >> otherwise complains that the source and destination pointer might > >> have different alignment restrictions. Removing the QEMU_PACKED should > >> be fine here since the structs are already naturally aligned. Anyway, > >> add some QEMU_BUILD_BUG_ON() statements to make sure that we've got > >> the right sizes (without padding in the structs). =20 > >=20 > > I missed these as well when getting rid of the false handling > > of failure of g_new0 calls. > >=20 > > Another alternative would be to point to the head structures rather > > than the containing structure - would avoid need to cast. > > That might be neater? Should I think also remove the alignment > > question? =20 >=20 > I gave it a try, but it does not help against the alignment issue, I stil= l get: >=20 > ../../devel/qemu/hw/mem/cxl_type3.c: In function=20 > =E2=80=98ct3_build_cdat_entries_for_mr=E2=80=99: > ../../devel/qemu/hw/mem/cxl_type3.c:138:34: error: taking address of pack= ed=20 > member of =E2=80=98struct CDATDsmas=E2=80=99 may result in an unaligned p= ointer value=20 > [-Werror=3Daddress-of-packed-member] > 138 | cdat_table[CT3_CDAT_DSMAS] =3D &dsmas->header; > | ^~~~~~~~~~~~~~ >=20 > From my experience, it's better anyway to avoid __attribute__((packed)) = on=20 > structures unless it is really really required. At least we should avoid = it=20 > as good as possible as long as we still support running QEMU on Sparc hos= ts=20 > (that don't support misaligned memory accesses), since otherwise you can = end=20 > up with non-working code there, see e.g.: >=20 > https://www.mail-archive.com/qemu-devel@nongnu.org/msg439899.html >=20 > or: >=20 > https://gitlab.com/qemu-project/qemu/-/commit/cb89b349074310ff9eb7ebe18a >=20 > Thus I'd rather prefer to keep this patch as it is right now. >=20 > Thomas Fair enough. Reviewed-by: Jonathan Cameron >=20 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D6C17C54E41 for ; Tue, 5 Mar 2024 15:53:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rhX6O-0002BX-Ro; Tue, 05 Mar 2024 10:53:14 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rhX5o-0001n3-CU; Tue, 05 Mar 2024 10:52:37 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rhX5l-0007X6-8k; Tue, 05 Mar 2024 10:52:36 -0500 Received: from mail.maildlp.com (unknown [172.18.186.31]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Tq0Lw2dv5z6J67f; Tue, 5 Mar 2024 23:47:36 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id 27DA9140F92; Tue, 5 Mar 2024 23:52:20 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Tue, 5 Mar 2024 15:52:19 +0000 Date: Tue, 5 Mar 2024 15:52:18 +0000 To: Thomas Huth CC: , Fan Ni , "Michael S. Tsirkin" , Marcel Apfelbaum , Subject: Re: [PATCH 3/3] hw/mem/cxl_type3: Fix problem with g_steal_pointer() Message-ID: <20240305155218.00000c00@Huawei.com> In-Reply-To: <4f6e1748-a917-4b2b-847d-fbfe04a3e43e@redhat.com> References: <20240304104406.59855-1-thuth@redhat.com> <20240304104406.59855-4-thuth@redhat.com> <20240304151037.00000f6c@Huawei.com> <4f6e1748-a917-4b2b-847d-fbfe04a3e43e@redhat.com> Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml100006.china.huawei.com (7.191.160.224) To lhrpeml500005.china.huawei.com (7.191.163.240) Received-SPF: pass client-ip=185.176.79.56; envelope-from=jonathan.cameron@huawei.com; helo=frasgout.his.huawei.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-to: Jonathan Cameron From: Jonathan Cameron via Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, 5 Mar 2024 08:27:52 +0100 Thomas Huth wrote: > On 04/03/2024 16.10, Jonathan Cameron wrote: > > On Mon, 4 Mar 2024 11:44:06 +0100 > > Thomas Huth wrote: > > =20 > >> When setting GLIB_VERSION_MAX_ALLOWED to GLIB_VERSION_2_58 or higher, > >> glib adds type safety checks to the g_steal_pointer() macro. This > >> triggers errors in the ct3_build_cdat_entries_for_mr() function which > >> uses the g_steal_pointer() for type-casting from one pointer type to > >> the other (which also looks quite weird since the local pointers have > >> all been declared with g_autofree though they are never freed here). > >> Fix it by using a proper typecast instead. For making this possible, we > >> have to remove the QEMU_PACKED attribute from some structs since GCC > >> otherwise complains that the source and destination pointer might > >> have different alignment restrictions. Removing the QEMU_PACKED should > >> be fine here since the structs are already naturally aligned. Anyway, > >> add some QEMU_BUILD_BUG_ON() statements to make sure that we've got > >> the right sizes (without padding in the structs). =20 > >=20 > > I missed these as well when getting rid of the false handling > > of failure of g_new0 calls. > >=20 > > Another alternative would be to point to the head structures rather > > than the containing structure - would avoid need to cast. > > That might be neater? Should I think also remove the alignment > > question? =20 >=20 > I gave it a try, but it does not help against the alignment issue, I stil= l get: >=20 > ../../devel/qemu/hw/mem/cxl_type3.c: In function=20 > =E2=80=98ct3_build_cdat_entries_for_mr=E2=80=99: > ../../devel/qemu/hw/mem/cxl_type3.c:138:34: error: taking address of pack= ed=20 > member of =E2=80=98struct CDATDsmas=E2=80=99 may result in an unaligned p= ointer value=20 > [-Werror=3Daddress-of-packed-member] > 138 | cdat_table[CT3_CDAT_DSMAS] =3D &dsmas->header; > | ^~~~~~~~~~~~~~ >=20 > From my experience, it's better anyway to avoid __attribute__((packed)) = on=20 > structures unless it is really really required. At least we should avoid = it=20 > as good as possible as long as we still support running QEMU on Sparc hos= ts=20 > (that don't support misaligned memory accesses), since otherwise you can = end=20 > up with non-working code there, see e.g.: >=20 > https://www.mail-archive.com/qemu-devel@nongnu.org/msg439899.html >=20 > or: >=20 > https://gitlab.com/qemu-project/qemu/-/commit/cb89b349074310ff9eb7ebe18a >=20 > Thus I'd rather prefer to keep this patch as it is right now. >=20 > Thomas Fair enough. Reviewed-by: Jonathan Cameron >=20